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Hawaiian Islands Synoptic Discussion and Guidance

502
FXHW60 PHFO 040142
AFDHFO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
400 PM HST FRI JUL 3 2015

.SYNOPSIS...
LIGHT TRADE WINDS WITH LOCALIZED LAND AND SEA BREEZES...AND A FEW
SHOWERS ARE IN STORE FOR INDEPENDENCE DAY. TRADE WINDS WILL BUILD
MONDAY AND TUESDAY...AND ARE EXPECTED TO REACH MODERATE LEVELS BY
THE MIDDLE OF NEXT WEEK. STRONG TRADES AND INCREASED SHOWER ACTIVITY
IS POSSIBLE DURING THE SECOND HALF OF THE WEEK.

&&

.DISCUSSION...
THE SURFACE RIDGE OVER THE ISLANDS CONTINUES TO LIFT TO THE NORTH
TODAY...AND WE ARE SEEING A RETURN TO EASTERLY WINDS IN THE
BACKGROUND FLOW NEAR THE BIG ISLAND AND MAUI COUNTY. NEAR
KAUAI...THE FLOW HAS TURNED A BIT MORE SOUTHEASTERLY THAN THIS
MORNING.

WITH THE RIDGE EXPECTED TO LIFT FURTHER NORTH TONIGHT...EXPECT LIGHT
TRADES TO BUILD BACK...HOWEVER SOME AREAS WILL LIKELY CONTINUE TO
SEE SOME LAND AND SEA BREEZES TOMORROW. LITTLE IN THE WAY OF
MOISTURE TO THE NORTHEAST OF THE ISLANDS...SO EXPECT SHOWER ACTIVITY
TOMORROW TO REMAIN LIMITED. SOME HIGH CLOUDS ARE EXTENDING OVER THE
ISLANDS FROM THE SOUTH.

AS THE RIDGE CONTINUE TO LIFT NORTH THROUGH MONDAY/TUESDAY...LOOK
FOR THE TRADES TO CONTINUE TO INCREASE TOWARDS MODERATE LEVELS. A
NEW HIGH MOVES IN NORTH OF THE ISLANDS MID WEEK...WHICH WILL HELP TO
FURTHER INCREASE THE TRADE WINDS.

THE GLOBAL MODELS ARE DEVELOPING A COUPLE LOWS FAR TO THE SOUTHEAST
OF THE ISLANDS DURING THE SECOND HALF OF THE WEEK WHICH BEAR
WATCHING. THE MODELS ARE KEYING OFF OF A FEW AREAS OF DEEP
CONVECTION. ONE SUCH AREA IS ABOUT 1200 MILES EAST SOUTHEAST OF
HILO...AND ANOTHER IS IS ABOUT 850 MILES SOUTH SOUTHEAST OF HILO.
BOTH THE GFS AND ECMWF BRIEFLY SHOW SIGNS OF DEVELOPMENT WITH THESE
AREAS...BUT KEEP THEM SOUTH OF THE ISLANDS. LOW LEVEL MOISTURE FROM
THESE SYSTEMS...PARTICULARLY THE ONE ABOUT 1200 MILES EAST SOUTHEAST
OF HILO...COULD EXTEND NORTHWARD AND BE CARRIED OVER THE ISLANDS
DURING THE SECOND HALF OF THE WEEK. IN ADDITION TO THE INCREASE IN
MOISTURE...AS THESE SYSTEMS PASS SOUTH OF THE ISLANDS...THEY WILL
HELP TO INCREASE THE PRESSURE GRADIENT OVER THE ISLANDS...HELPING TO
INCREASE THE TRADE WINDS.

NHC IS MONITORING AN AREA MUCH FURTHER EAST...ABOUT 2400 MILES EAST
SOUTHEAST OF HILO...AND THE ECMWF IS MUCH MORE AGGRESSIVE THAN THE
GFS WITH DEVELOPING THIS AREA LATER IN THE WEEK. WE WILL BE CLOSELY
MONITORING THESE AREAS...BUT IT IS STILL SEVERAL DAYS TO BE SURE OF
ANYTHING...PARTICULARLY WITH THE DIFFERENCES IN THE MODELS.

&&

.AVIATION...
TRADE WINDS WILL CONTINUE TO RETURN THROUGH THE WEEKEND AS THE
RIDGE MOVES NORTH OF THE STATE. LOCALIZED LAND BREEZES WILL HELP
CLEAR OUT MOST AREAS OVERNIGHT. ANY CLOUDS AND SHOWERS SHOULD
REMAIN PREDOMINATELY VFR AND WILL FAVOR WINDWARD AND MAUKA AREAS.
OVERALL...VFR WILL PREVAIL.

&&

.MARINE...
SMALL CRAFT ADVISORY /SCA/ CONDITIONS ARE NOT EXPECTED THROUGH THE
HOLIDAY WEEKEND. WITH THE TRADES BUILDING IN MONDAY AND
TUESDAY...SCA DEVELOP THE WINDIER MARINE ZONES...AND THEN EXPAND TO
OTHER AREAS AS THE TRADES BUILD FURTHER.

ANOTHER SOUTH SWELL IS EXPECTED TO ARRIVE SATURDAY
NIGHT/SUNDAY...AND THEN SLOWLY DECLINE MONDAY. THIS SWELL COULD
BRING SURF ALONG THE SOUTH FACING SHORES NEAR ADVISORY LEVELS.
ANOTHER SOUTHERLY SWELL IS EXPECTED TO REACH THE ISLANDS
MONDAY...PEAK TUESDAY AND THEN DECLINE ON WEDNESDAY. SEE THE LATEST
SURF FORECAST DISCUSSION FOR FURTHER DETAILS.

THE CURRENT NORTHWEST SWELL WILL GRADUALLY DECLINE THROUGH THE
WEEKEND. ANOTHER SMALL NORTHWEST BUMP MAY ARRIVE ON MONDAY NIGHT.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
NONE.

&&

$$

DISCUSSION/MARINE...M BALLARD
AVIATION...EATON



Bulletins, Forecasts and Observations are courtesy of Honolulu National Weather Service Forecast Office